Night-flowering orchid (Bulbophyllum nocturnum)

The night-flowering orchid is the only orchid species to open its flowers at night and close them during the day.

First described in 2011, the night-flowering orchid is known only from the island of New Britain, in Papua New Guinea.

The night-flowering orchid is an epiphytic species, meaning it grows on trees or other plants.

The night-flowering orchid is thought to be pollinated by small, nocturnal flies, which it attracts using strange appendages on the petals.

The night-flowering orchid has yet to be classified by the IUCN, but is listed on Appendix II of CITES (3).

First described as recently as 2011, the night-flowering orchid (Bulbophyllum nocturnum) is the only known example of an orchid which opens its flowers only at night, closing them during the day. When the first specimens of the night-flowering orchid were grown in cultivation they soon produced flower buds, but the buds appeared to abort the night before they were expected to open. Only when the plant was observed at night were its unusual flowering habits revealed (1) (2).

The flowers of the night-flowering orchid measure about 2.5 centimetres across (2) and consist of tiny petals surrounded by three relatively narrow sepals, which are yellowish-green with a red tinge at the base (1) (2). As in a number of other closely related Bulbophyllum species, the flowers of the night-flowering orchid are unusual in having bizarre, intricate appendages on the petals. In this particular species, these are long, greyish and thread-like, measuring up to 0.8 centimetres in length (1) (2), and are suspended on extremely fine, thread-like stalks (1).

Like other orchids, the night-flowering orchid has a petal which is modified into a ‘landing pad’ for pollinators (4) (5). Known as the ‘lip’, it is dark red in this species (1) (2) and is made up of three lobes (1). The male and female reproductive organs of orchid flowers are fused into a single structure known as the ‘column’ (4) (5). In the night-flowering orchid, this is around 2.4 millimetres in length and is yellow with a reddish tinge. The flowers of the night-flowering orchid are not reported to have a noticeable smell (1).

The leaves of the night-flowering orchid grow from hanging, stem-like rhizomes, which may measure up to 15 centimetres in length. The rhizomes possess enlarged sections known as ‘pseudobulbs’, which store water and carbohydrates. The leaves of the night-flowering orchid are oval in shape, and measure up to about six centimetres in length and three centimetres in width (1) (2).

The night-flowering orchid is known only from the island of New Britain, in Papua New Guinea (1) (2).

An epiphytic species, the night-flowering orchid grows on trees or other plants. This orchid inhabits rainforests at elevations of 240 to 300 metres (1) (2).

In cultivation, the night-flowering orchid has been found to open its flowers at about 10pm and to close them around 12 hours later. The flowers of this species are short-lived, lasting for just a single night (1) (2). It is not yet known whether the night-flowering orchid opens and closes its flowers at a slightly different time in the wild (1).

Like related Bulbophyllum species, the night-flowering orchid is likely to be pollinated by small flies. The unusual appendages on the petals are thought to attract these flies, probably by mimicking fungi or the fruiting bodies of slime moulds (1) (2) (6). Although it is not yet known for certain why the night-flowering orchid opens its flowers at night, it is likely that the flies that pollinate this species are nocturnal (1) (6).

Little other information is currently available on the life cycle of the night-flowering orchid, but like other orchid species it is likely to produce vast numbers of tiny seeds. These minute seeds have virtually no energy reserves, and can only germinate with the help of a fungus with which the orchid forms a symbiotic relationship (4) (5).

The night-flowering orchid is still quite poorly known, and its conservation status has yet to be assessed by the IUCN. However, this newly discovered plant may potentially be threatened by the logging of its rainforest habitat (2) (6). The night-flowering orchid is not thought to be very widespread, although further field studies would be needed to confirm this (2).

There are no specific conservation measures currently known to be in place for the night-flowering orchid. However, like other orchids it is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that international trade in this species should be carefully controlled (3).

The night-flowering orchid has been grown in cultivation in the Hortus Botanicus Leiden, in the Netherlands (2).

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: arkive@wildscreen.org.uk

Epiphyte: a plant that grows on another plant, typically a tree, using it for physical support but not drawing nourishment from it.

Germinate: to begin to grow, usually following a period of dormancy and in response to favourable conditions. For example, the sprouting of a seedling from a seed.

Nocturnal: active at night.

Pollinate: to transfer pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.

Pollinator: an animal that in the act of visiting a plant’s flowers transfers pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.

Rhizome: a horizontal plant stem, usually underground, which produces roots and shoots.

Sepal: a floral leaf (collectively comprising the calyx of the flower) that forms the protective outer layer of a flower bud.

Slime mould: a fungus-like organism that uses spores to reproduce.

Symbiotic relationship: relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).